The invention resides in a worm-like operating mechanism actuated by pneumatic or hydraulic pressure fluids for lifting, fixing, grasping and moving objects. The mechanism is stretchable and/or pivotable in any direction. It includes pressurized fluid-operated actuators, which automatically return to their rest position when the pressurized fluid is released. Such mechanisms are suitable for forming robot arms, artificial limbs or controllable movable parts for medical instruments.
Operating mechanisms known presently for those applications are relatively complicated and expensive and provide only for limited movability or relatively small force transmission.
DE 39 18 955 A1 discloses mechanism corresponding in principle to a muscle. It includes a balloon-like container consisting of a flexible skin with a pump for pumping a fluid into, or out of, the balloon-like container. The balloon is surrounded by a net, which can be extended lengthwise up to a maximum length at which point the balloon enclosed by the net completely contracted and has no internal volume. When the balloon is filled to its maximum volume the ends of the net are pulled together to a minimum distance. The net then firmly engages the balloon and prevents a destructive further expansion. With this arrangement, a joint-like elbow can be operated, however, movement is limited to one degree of freedom.
Actuators of the artificial muscle type are described in GB 2 240 083 A. They include channel-like elements which can assume any spatial state between a total collapse (zero volume) and a fully expanded state (maximum volume). They include desired fold areas. By filling or emptying the channels the desired volume states can be obtained. By arranging these elements in series, arm- or tentacle-like structures can be formed. The channels are enclosed by, or embedded in, support foils which limit volume expansion.
WO 90/15697 shows plug-like shapes, which can be operated by pressurized fluid such that stretch or bending motions are produced. Channel-like structures are connected for this purpose to other foils such that, upon filling, the whole structure assumes a predetermined shape. The movement of the structure however has only a single degree of freedom starting with a folded limp structure and leading to an expanded taut structure and vice versa.
DE 196 17 852 A1 discloses a method of making fluid operated miniature manipulators employing expandable pocket structures comprising two foils disposed on top of each other. The foils are welded together along a line and include a supply passage for the admission and the discharge of fluid. They can assume any volume between zero and a maximum volume. The various designs illustrated however do not permit any tilting motion either, that is, they have only one degree of freedom.
It is the object of the present invention to provide an operating mechanism for generating spatial tilt and linear movements which mechanism is capable of generating large movements and large forces.